The present invention relates to a superconducting power-transmission cable using superconductive materials, and in particular, to a superconducting power-transmission cable of which conductor layers and shielding layers are adjusted in both winding pitchs and winding directions.
In superconducting cables for transmitting power with less loss, a conductor is formed by winding tape-shaped superconducting wires around a core or the like in spiral forms, so that flexibility is given to the cable itself. When the cable is required to transmit a large amount of current, the number of layers in the conductor is increased so as to form multi-layered conductor, thus increasing current capacity. Furthermore, in order that an electromagnetic field generated by current flowing through the conductor is avoided from leaking out of the cable, an insulator is formed on and around the outer surface of the conductor, and then tape-shaped superconducting wires are wound on and around the insulator in a spiral form to form shielding layers. The number of those wound wires in the shielding layers is almost the same as that of the conductors, thus containing the electromagnetic field within the cable.
Japanese Patent Provisional Publication No. 62-180910 publication discloses a superconducting cable, which is formed by winding a complex multi-filamentary superconducting member in spiral forms around the outer surface of a normal conducting member so that right-handed wound layers and left-handed wound layers are formed alternately thereon.
Moreover, Japanese Patent Provisional Publication No. 8-287746 publication discloses a superconducting cable for alternating current, in which a plurality of layers of tape-shaped superconducting wires are wound around a center member. In the superconducting cable, the winding pitch of the wires becomes larger as the windings proceed to outer layers, in order to make all the layers equal in inductance to each other.
Moreover, Japanese Patent Provisional Publication No. 9-45150 publication discloses a multi-layer superconductor, in which a superconducting wires are wound in spiral forms around a core to form a plurality of layers. In the multi-layer superconductor, a maximum of the winding pitch is specified, and the winding pitch becomes shorter as the winding proceeds from an inner layer to an outer layer.
One embodiment of the superconducting cable for alternating current according to the present invention is a superconducting cable for alternating current comprising conductor layers formed by a plurality of tape-shaped superconducting wires wound around a center member, an electric insulating layer formed outside the conductor layers, and a plurality of shielding layers formed outside the insulating layers, wherein the cable comprises:
(a) the conductor layers being formed, where N is the number of layers in the conductor layers and expressed by an integer, by gradually increasing a winding pitch of conductor layers in the same direction from an inner first layer to an N/2 layer when the number of layers is even, or from an inner first layer to a (Nxe2x88x921)/2 layer when the number of layers is odd, and then by gradually decreasing the winding pitch of conductor layers, in an opposite direction to the inner layers, from a N/2+1 layer to an N layer when the number of layers is even, or from a (N+1)/2 layer to an N layer when the number of layers is odd; and
(b) the shielding layers being formed, where n is the number of layers in the shielding layers and expressed by an integer, by gradually increasing a winding pitch of shielding layers in the same direction from an inner first layer to an n/2 layer when the number of layers is even, or from an inner first layer to a (nxe2x88x921)/2 layer when the number of layers is odd, and then by gradually decreasing the winding pitch of shielding layers, in an opposite direction to the inner layers, from a n/2+1 layer to an n layer when the number of layers is even, or from a (n+1)/2 layer to an n layer when the number of layers is odd.